A. A method of oil, gas and hydrogeological wells production rate increase is adopted as analogous. That method was described in U.S. Pat. No. 6,651,741 published on Apr. 17, 2003. The method includes slot perforation of the production casing and stratum only in the vicinity of the borehole and pumping treating fluid in the well and key seat. Slot perforation is performed with the use of a hydroperforator within the interval of lowest inflow values by developing two diametral oppositely oriented slot key seats in the stratum. With all advantages of this method, it is not free of shortcomings. The main shortcoming is that in the process of perforating, jet pressure does not pulsate. That, in turn, reduces the force the jet applies to the stratum surface being treated, lowers perforation efficiency, and as a result, requires extra time of perforator operation.
B. An analogous method of increasing the productive stratum permeability is also known (USSR Author's Certificate # 1369379, published on Dec. 10, 1996). The method includes creation of vertical discharge slots in the well. This method, as well as the previous mentioned, has the same shortcoming: jet pressure does not pulsate, thus requiring extra time of perforator operation.
C. As well, an analogous method is known of increasing the well production rate, which is put forward in the Russian Federation Patent 2190759 published on Oct. 10, 2002, entitled “Hydraulic perforator”. The perforator design was improved in comparison with the previous analogous methods, thanks to the pressure pulsator with which the perforator was equipped. In this analogous method is included pumping of liquid with abrasive material under pressure into the pipe string and hydroperforator; liquid with abrasive material impacts the well elements and the stratum via the hydroperforator hydromonitor nozzle; when the liquid with abrasive material impacts the well elements and the stratum, pressure changes in the pipe string deliver liquid with abrasive material.
This analogous method also has essential shortcomings. For example, when it is implemented, pressure oscillations are generated at one frequency only, and, should the pulsator operating frequency be equal to the natural oscillation frequency of any equipment element, the pulsator operating frequency cannot be changed. The work using such a method does not reduce the risk of resonance and of breakdown equipment breakdown.
D. As the prototype of the disclosed method of well production rate increase, we adopt the known invention per the Russian Federation Patent 2061847 published on Jun. 10, 1996 and entitled “Pulse hydraulic perforator”. In the named patent, a method of well production rate increase and of perforator efficiency enhancement is described. The method (prototype) of well production rate increase, includes lowering the hydroperforator equipped with hydromonitor nozzles into the well on the pipe string; pumping liquid with abrasive material under pressure into the pipe string and hydroperforator; and impacting the well elements and the stratum with the liquid with abrasive material via hydroperforator hydromonitor nozzles. When the liquid with abrasive material impacts the well elements and the stratum, pressure is changed in the pipe string, delivering the liquid with abrasive material. The hydroperforator contains the pressure pulses generator. The pressure pulses generator, in the process of its operation, ensures the increase of the effect of the perforating jet of liquid on the stratum surface being crushed, as well as its impact on the deep-seated layers of the stratum adjacent to the key seat surface, thanks to pressure oscillations. The pressure pulses also spread upwards, towards the wellhead, in the liquid flowing from the wellhead to the perforator along the tubing string (TS) column.
The features of the prototype which coincide with the features of the method of well production rate increase disclosed in the present application, are as follows:
a) the method of well production rate increase;
b) lowering the hydroperforator equipped with hydromonitor nozzles into the well on the pipe string;
c) pumping liquid with abrasive material under pressure into the pipe string and hydroperforator;
d) impacting the well elements and the stratum with the liquid with abrasive material via hydroperforator hydromonitor nozzles;
e) when liquid with abrasive material impacts the well elements and the stratum, pressure is changed in the pipe string delivering the liquid with abrasive material.
The shortcoming of the prototype is the fact that when it is implemented, pressure oscillations are generated at one frequency only, thus ensuring effective impact only on the minor part of the stratum inner layers adjacent to the key seat surface. As it is known, the fixed frequency of pressure oscillations results in the fixed depth of the mud-pulse impact on the stratum. The impact depth is inversely proportional to the square root of the oscillations frequency (see Russian Federation Patent 2162509 published on Jan. 27, 2001).
Another significant shortcoming of the prototype is the fact that, should the pulsator operating frequency be equal to the natural oscillation frequency of any equipment element (TS, pumping units, perforator, fittings, etc.), the frequency of generated pressure pulses cannot be changed, thus possibly causing the equipment element to operate in the resonance mode. Keeping in mind that the perforation time can last up to several hours, breakdown of the equipment operating in the resonance mode becomes possible, and that occurs frequently in the process of operating such perforators. TS rupture in the resonance mode and its destruction before the bottom hole may cause loss of the well.
In addition, sequence of work and characteristics of impact on the well elements and on the stratum were not optimized in the prototype. Some operations could be combined. For example, stratum perforation and impact on the stratum layers adjacent to the key seat surface could be performed simultaneously. That, in turn, would increase production performance in the future and would reduce the overall time of operations required to recover the well.